The present invention relates to a microwave oven of a type having a door locking mechanism.
In most microwave ovens, an interlocking mechanism is generally employed for rendering a high frequency wave oscillator, for example, a magnetron, inoperative when a door, which has been in position to close an access opening communicating with the oven chamber, is opened during operation of the high frequency wave oscillator. The interlocking mechanism employed for this purpose is mainly composed of a switch for opening an electric circuit of the high frequency wave oscillator and a door key provided in the door for operating the switch. Accordingly, in a condition wherein the door is closed, the door is locked in the closed position by the door key.
The door employed in most microwave ovens heretofore commercially available tends to warp or deform when it receives an external force, the value of which external force varies depending upon the type of material for the door. Accordingly, for example, when the door is to be opened without the door key properly handled during closure of the door, the door tends to deform by the application of an external force applied to the door so as to open the latter. Moreover, since the interlocking mechanism is not completely released under this condition, the high frequency wave oscillator continues radiating a high-frequency electromagnetic energy or microwave into the oven chamber. As a result thereof, a gap is formed between the door and a portion of an oven casing structure located around the access opening, from which gap leakage of high-frequency electromagnetic energy will occur. As is well known to those skilled in the art, leakage of the high-frequency electromagnetic energy is hazardous to the human body.
A similar condition as hereinabove described will occur even when a foreign matter, for example, a piece of paper, towel and napkin, is caught or jammed in between the door and that portion of the oven casing structure as the door is closed and/or when a solidified body of spillage of food particles and grease spatterings piles on one or both of the door and that portion of the oven casing structure while the microwave oven is frequently used for a substantially long period of time. When the door is forcibly closed jamming a piece of paper, towel or napkin or a solidified body of spillage of food particles or grease spatterings between the door and that portion of the casing structure, the door tends to deform, thereby forming a gap between the door and that portion of the oven casing structure while it is held in the closed position and the door key is in position to operate the switch. If the high frequency wave oscillator is operated under this condition, a user or operator of the microwave oven is susceptible to high-frequency electromagnetic energy leaking through the gap thus formed between the door and that portion of the oven casing structure.
Furthermore, most users or operators of the microwave oven seldom follow a how-to-use instructions furnished by the manufacturer and, therefore, during normal use, a piece of napkin or towel which is frequently used in kitchens is often jammed in between the door of the oven and that portion of the oven casing structure. What is jammed in between the door of the microwave oven and that portion of the oven casing structure is not always limited to that described above, but it may include chopsticks, toothpicks, and a spillage of food particulars which may remain unremoved and is solidified because of insufficient cleaning of the microwave oven interior. It is true that the greater the gap, the greater the amount of microwave leakage, and the leakage of microwave energy should be strictly avoided.